Abstract
The energy dissipation rate and interfacial thermal conductance between two sliding surfaces are important to accurately predict the interface temperature rise, while their physical mechanism is not well understood. In this study the energy dissipation and interfacial thermal transport between a sliding silicon film and a fixed silicon substrate are investigated by molecular dynamics simulations. The results show that the mean friction force first increases with increasing normal load. However, when the normal load exceeds the critical value of about 60 eV/Å, the interface atoms begin to collapse, causing the mean friction force to drop with the further increase of the normal load. Our study also shows that the energy dissipated during the friction process is quantitatively equal to the conducted heat. By extracting the interfacial temperature difference, it is found that the interfacial thermal conductance in sliding state is 2∼4 times higher than that in static state with the same normal load from 10 to 60 eV/Å. This is because the interfacial atoms suffer great dynamic impacts during the friction process, which excites more non-equilibrium phonons and helps to enhance the phonon interfacial transmission coefficient. The present investigation demonstrates that the dynamic excitation induced by the friction process can modify the interfacial thermal conductance, which would be of great significance to accurately predict the temperature rise of the sliding interface.
Highlights
In many important applications, such as the braking system[1,2] and dynamics sealing system,[3] the prediction of surface temperature is critical because the high surface temperature due to friction heating would affect the reliability and stability of the mechanical components
After building the atomic models, we investigate the relation between the interface friction force and the normal load
In various sliding velocities from 10 to 50 m/s, the mean friction force shows a first increase with increasing normal load, and rapid decrease with further increasing the normal load
Summary
In many important applications, such as the braking system[1,2] and dynamics sealing system,[3] the prediction of surface temperature is critical because the high surface temperature due to friction heating would affect the reliability and stability of the mechanical components. It has been believed that the friction force and interfacial thermal resistance strongly depend on the load and the contact condition of the interface, but the underlying physical mechanism is not clear. It is still a big challenge to predict the temperature rise of the frictional interface due to the unknown interfacial energy dissipation and thermal resistance. Lee et al[19] has attributed the higher interface friction force to the lower interfacial thermal resistance in their experiment, since lower interfacial thermal resistance can help to transfer the heat much more efficiently. The above experiments[18,19] don’t establish the relation between the dissipated energy during the sliding process and the conducted heat across the interface. The sliding process may change the interfacial thermal resistance,[20] but the associated mechanism with phonons is still not known.
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